Engagement coordination for advanced missile defense systems is subject to sensor registration errors occurring during handover between each system. Thus, the sensors require registration in order to reduce such registration errors during handover. In addition, each sensing system or element will need to angularly register its sensors to local geodetic coordinate systems in order to minimize the tracking and guidance errors and to provide additional margin to the associated weapon system's pointing and divert error budgets. “Divert” is the amount of position error a weapon can “take out” or accommodate during the terminal guidance phase.
FIG. 1 is a simplified perspective or isometric view of a ship 10 with an array 12 of radar faces 14a, 14b, illustrating the pointing and divert errors due to radar face bias registration error. In FIG. 1, the true position of a target to be defended against is illustrated as 16t, and the true position of a missile for engaging the target is illustrated as 18t. The actual line-of-sight between the radar face 14b and the target and missile are designated as 17t and 19t, respectively. In addition to the yaw, pitch and roll motion of the ship, which may introduce errors into the target and missile tracking systems, radar face angular registration errors, illustrated by an incremental angle δθ, result in apparent target and missile lines-of-sight designated 21a and 23a, respectively. Thus, the relative directions in which the target and the missile are sensed relative to the ship 10 differ from the actual directions.
The incremental error angle δθ not only results in a different apparent direction of the target and missile, but also results in a different apparent heading. This may be understood by considering missile 18t of FIG. 1, which may be considered as heading along the actual line-of-sight path 19t. Since the registration error δθ makes the apparent line-of-sight diverge from the actual line-of-sight, it also makes the missile heading appear to differ from the actual heading by δθ, so that the apparent heading of the missile does not coincide with the actual heading, as suggested by missile symbol 18ah. For the same reasons, the apparent heading of the target is illustrated as 16ah, and differs from the actual target heading.
In addition to the errors in apparent heading of the target and the missile in FIG. 1, the face angular registration errors δθ also tend to cause an apparent translation error in the positions of the target and the missile. In FIG. 1, the apparent target location is shown as 16al, lying along apparent line-of-sight 21a, and the apparent missile location is shown as 18al, lying along apparent line-of-sight 23a. Thus, both the apparent lines-of-sight and the apparent headings of the target and the missile differ from the actual values due to misregistration of the radar system faces.
Current technology in system bias registration relies on pre-engagement (non-real-time) algorithms that require supplemental data such as satellite ephemeris to provide a reference for the registration bias estimation. ARCHER is such an algorithm. ARCHER was developed by Nichols Research, part of Computer Science Corporation (CSC), the address of which is 333 W. El Camino Real, Sunnyvale, Calif. These registration algorithms provide sensor bias registration during non-tactical engagement periods, sometimes hours or days prior to the tactical engagement. Such time differences may reduce the quality or effectiveness of the registration due to latency and also due to the fact that the biases are time varying, sometimes on the order of minutes, depending on the time of day and the environment.
Improved and or alternative target tracking and sensor registration systems are desired.